Tires are a part of your car's suspension system, and their manufacturers design them to work with it to give you a smooth ride under as many conditions and at as many speeds as possible. A shimmy is when your car shakes or vibrates from side to side, either very noticeably, or almost imperceptibly. It may feel as though your car's body and wheels are not working together. Your Subaru Forester's shimmying is the result of some basic problems or challenges.
Lack of tire balance is the most common cause for shimmy on the Subaru Forester front end, especially if it is felt only at certain speeds. This is a gyroscopic effect caused by tire rotation. Even if your tires were balanced when you purchased them, it is fairly easy for wheel weights to get jarred loose and fall off on bumpy roads. Have your tire balance checked by a reputable tire shop.
Check your axle balance. If your CV axles have been recently replaced, you may have a poorly balanced axle. Re-manufactured axles are notoriously unreliable in Subaru Foresters. Also, there is a measurement for axle backlash. If the old axle was not replaced exactly as the original, the backlash, or spacing may be off. Check with a Subaru dealer, or a Subaru specialty shop to find the measurement, and determine if this is the problem.
Shimmy can also be the result of faulty suspension components. On the Forester, the most common is a faulty or bent tie-rod end. If the tires and axles are balanced, elevate the front end of the vehicle, and physically check all suspension components. Have an assistant turn the wheels from side to side. If there is any play in the steering, shimmy will result.
